The present invention relates to a lockset and, more particularly, to a lock cylinder which promotes a burglarproof effect.
A type of conventional anti-theft lock cylinder for locks is generally includes an outer housing and an inner key plug rotatably received in the housing about an axis and having a keyway centrally extending along the axis. The housing and the key plug are internally provided with a plurality of tumbler pins for locking the key plug in the housing, thereby preventing unauthorized operation of the lock cylinder. When a special or corresponding key is inserted into the keyway of the key plug, the tumbler pins are lifted to a shear line between the housing and the key plug, allowing the key plug to be rotated relative to the housing to unlock the lock cylinder.
The lock cylinder mounted inside a lock is a sophisticated precise device with a critical function to prevent the lock from being easily and quickly unlocked by a burglar. One burglar or habitual thief, however, is still capable of easily unlocking the lock with a picking tool because the lock cylinder based on the prior art is equipped with a single key plug having a flat or cross keyway and, thus, is easily unlocked by the burglar who gradually inserts the picking tool into the keyway of the key plug. Specifically, those internal components of the lock cylinder are symmetrically arranged therein and will not be changed in their relative positions despite a turning action of the key plug relative to the housing in the process of inserting the picking tool into the keyway, failing to hinder the picking tool's constant probing to unlock the lock cylinder.